Emergency Core Cooling Systems (ECCS) of nuclear power plants typically include strainers (e.g., screens or other coarse filters) designed for preventing large debris generated by a Loss of Coolant Accident (LOCA) from reaching the ECCS pumps and/or components located downstream of the ECCS pumps. For some ECCS strainers, the holes in the strainer's surface material may range from 0.035 inch diameter holes up to 0.125 inch diameter holes, depending on plant-specific conditions. Although most debris may be stopped by an ECCS strainer, there may be “fine” debris that is small enough to flow through the ECCS strainer, even after a debris bed is formed on the surface of the ECCS strainer. If there is an excess of the fine debris and/or if the debris is of the wrong size and/or type, the debris could damage the ECCS pumps and/or increase the head loss of the system, which could cause insufficient flow of cooling water inside the reactor. This is not allowed to happen for safe operation of a nuclear power plant.
More specifically, a nuclear reactor is typically contained in a containment building, and if a LOCA in the form of a high energy pipe explosion were to occur, the generated debris would fall or be washed down to the basement of the containment building where a pool of water would form. Some of the fine debris in the pool of water may be in the form of fibrous insulation that falls off of piping and other components within the containment building during the LOCA. The pool supplies the ECCS pumps with the water needed to keep the reactor cool and to operate water sprays that condense the steam inside the containment's closed atmosphere. As the ECCS pumps receive water from the pool, water in the pool is drawn through the ECCS strainers. Some of the fine debris that is suspended in the water will flow through the ECCS strainers and reach components downstream of the ECCS strainers, such as valves, pumps, spray nozzles, the reactor vessel, etc. Damage to the downstream components and/or blockage of recirculation in the reactor vessel may occur if too much fine debris passes through the ECCS strainers.
In accordance with one aspect of this disclosure, there is a desire to collect a sufficient quantity of fine debris (e.g., fibrous debris) that would otherwise flow through the ECCS strainers, while at the same time limiting any head loss for the ECCS pumps.